'Stratolaunch' test puts billionaire's giant jet through its paces

Double-bodied aircraft to become launch platform for rockets boosting satellites into orbit.

Stratolaunch completes first low-speed taxi test.Bennett Sell-Kline

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Dec. 21, 2017, 4:03 PM GMT / Updated Dec. 21, 2017, 4:03 PM GMT

By Megan Gannon, Live Science

Stratolaunch's rocket-launching mothership was driven down the runway for the first time this past weekend.

The double-bodied jet — which has the largest wingspan of any aircraft in the world — has been undergoing tests at Stratolaunch's facility at the Mojave Air and Space Port in California. The latest phase in this process was testing the aircraft's steering and stopping capabilities.

Video footage of the taxi test showed the plane rolling along at a slow speed. Afterward, Stratolaunch officials said the vehicle's steering, braking, anti-skid and telemetry systems all operated as anticipated.

"Our crew was able to demonstrate ground directional control with nose gear steering, and our brake systems were exercised successfully on the runway,"George Bugg, Stratolaunch's aircraft program manager, said in a statement. "Our first low speed taxi test is a very important step toward first flight. We are all proud and excited." [Supersonic! The 11 Fastest Military Airplanes]

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The private spaceflight company Stratolaunch is the brainchild of Microsoft co-founder Paul Allen. The carrier plane is designed to make a runway-style takeoff and then, at cruising altitude, deploy rockets that can launch small satellites into low-Earth orbit.

The aircraft weighs 500,000 lbs. (227,000 kilograms), and it can carry another 550,000 lbs. (almost 250,000 kg) with up to three rockets under the conjoined wing at the center of the vehicle. Its wingspan is longer than a football field, measuring 386 feet (118 meters) across.

The aircraft was built by Scaled Composites, the Mojave-based aerospace company founded by spaceship builder Burt Rutan. Scaled Composites is also behind the design for White Knight Two, the mothership built to launch Virgin Galactic’s tourist-carrying space plane.